There is currently no standard therapy for patients with GBM whose tumors recur following surgery, radiotherapy, and adjuvant nitrosourea chemotherapy. SU101 is an inhibitor of signal transduction events which follow binding of platelet-derived growth factor to its receptor. SU101 has been shown to inhibit the growth of glioma cells in experimental systems. The present study is Phase III multicenter trial to compare the median survival of patients with GBM at first relapse when treated with either SU101 or oral procarbazine. Patients will be stratified for age, performance status, and time from the initial diagnosis to tumor recurrence. Patients will undergo serial neurologic examinations and contrast-enhanced MR scans to provide objective assessments of tumor response and progression. The primary endpoint will be median survival dated from initiation of SU101 or procarbazine. Secondary endpoints will be objective tumor response and median time to tumor progression in the two treatment arms. Standardized quality of life assessments will also be carried out. The GCRC will be utilized for outpatient intravenous infusion of SU101.